The field of art to which this invention pertain is radiation curable compositions.
Due to environmental concerns and the high cost of solvents, commercial interest in radiation curable compositions is constantly increasing. Legislation which restricts the amount of solvent and other pollutants that can be vented to the atmosphere is one reason for this increased interest. Other reasons are the concerns expressed by unions and individuals over the possible toxic effects of prolonged exposure to volatile organic materials and also the high cost of petroleum derived solvents. Generally, radiation curable system are essentially 100 percent reactive systems, i.e., substantially all of the component react to produce the final product. Such systems can be cured by exposure to high energy ionizing radiation or to actinic radiation in the presence of photoinitiators.
Various types of ethylenically unsaturated compounds have been used in making radiation curable compositions. Examples of such compounds include acrylated epoxides, such as those described in U.S. Pat. Nos. 3,676,398, 3,770,602, 4,072,592 and 4,511,732. Acrylated urethanes, such as those described in U.S. Pat. No. 3,700,643 and U.S. Pat. No. 4,511,732, have also been used in radiation curable composition. Norbornene polymers, such as those described in U.S. Pat. No. 3,554,886, are examples of other types of radiation curable compositions. Radiation curable coating compositions made from copolymers of 4-acetoxystyrene are described in U.S. Pat. Nos. 4,826,890 and 4,826,891. Constant efforts are being made to find other compositions which can be used in radiation curing.